A contested race is shaping up for two Board of Selectmen seats on this spring’s annual town election ballot. Jason J. Kreil, an alternate member of the Planning Board and a former full voting member of the board, has taken out nomination papers for the position. He would join Timothy M. Caldwell, who also ran for a selectman’s seat in a June special election, and incumbent David Gavin on the May 6 ballot. Voters will also fill two seats on the School Committee, a seat on the Library Board of Trustees, and the town moderator’s position. The deadline for obtaining nomination papers from the town clerk’s office is March 14.